The word subieses is the imperfect subjunctive form of subir in the second person singular. There are other translations for this conjugation.
See the full subir conjugation

subir

Tal vez si no subieses a Londres todos los fines de semana.
Perhaps if you didn't go up to London every weekend.
Me gustaría que subieses a mi despacho.
I'd like you to come up to my study.
No esperaba que subieses tú la cena.
I do not think you get to make your dinner.
Así que me gustaría que volvieses al ascensor, John, y subieses.
So I'd like you to get on the elevator, John, and go back up.
Bien, quisiera que subieses, pero...
Well, I wish I could ask you up, but...
Rosanna estaba aquí antes de que subieses a tu reunión de socios.
Rosanna was here earlier when you went upstairs for your partner meeting.
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